Touching the Future: Artificial Skin Isn't Sci-Fi

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A whisper-thin new pressure sensor could be a step toward
creating artificial skin that is able to actually feel.

A sense of touch is important for developing robots that can
navigate the world, and could improve prosthetic limbs for
amputees. But artificial human skin is remarkably difficult to
engineer, given that skin is sensitive to the lightest of
touches, flexible and uses little energy.

A new sensor may fit that bill, according to a paper published
today (May 14) in the journal Nature Communications. The sensor
is more sensitive to pressure than human skin, said study
researcher Zhenan Bao, a professor of chemical engineering at
Stanford University. [ Bionic
Humans: Top 10 Technologies ]

"If you use your finger to touch your
skin or hand, the pressure applied is in the kilopascal
range," Bao told LiveScience, referring to a unit of pressure.
"Our sensor can detect pressure that is a few hundred times less
than that gentle touch."

Bao and her colleagues have been working on electronics inspired
by human skin for years. In 2010, they announced the development
of an extra-sensitive pressure sensor made with ultrathin rubber.
But that device didn't have a flexible transistor, which is the
semiconductor
that transmits the signal from the sensor.

The new device is a transistor made of a flexible polymer
semiconductor, Bao said.

"If we have a layer of rubber, and we apply pressure onto the
rubber, the rubber will deform," she said. "And when it deforms,
it will change the amount of charge it can store. These charges
will impact the current flow into the transistor."

The sensor works even when curved, as around a body part. Bao and
her colleagues tested their device on a man's wrist, and found
they could take his pulse with more far more sensitivity than by
laying fingers on his artery.

Fingers held to a pulse point can only detect the strongest push
of blood through a vessel. The flexible sensor can also detect a
second, weaker wave of blood being bounced back from the
extremities, and a third wave that can provide a measurement of
the stiffness of the artery. Stiff arteries can be a sign of
damage from diabetes, or cholesterol buildup.

The next step for Bao and her co-researchers is to make the
device wireless, and thus less cumbersome for continuous medical
monitoring. Ultimately, she said, the goal is to enter sci-fi
territory: building artificial skin that can sense and feel.

"To actually make artificial skin, we still need to be able to
connect the sensors with neurosystems, so that the
sensor signal can be transmitted to the human brain," Bao
said. "That will be a big challenge."

Nevertheless, she said, the team is making progress. In 2011,
they developed a stretchable touch sensor, and in 2012, they
created a version that could self-heal from scratches.

"My students love 'Star Trek' and 'Iron Man,'" Bao said. "Those
science fiction movies give them inspiration, and make us more
innovative and creative."